The goal of this project is to investigate the aversive conditioning of environmental stimuli by illness. Of special interest is the phenomenon of "potentiation" in taste-aversion learning. Potentiation in this situation occurs when a taste-illness pairing facilitates the conditioning of environmental cues surrounding the food. Instead of overshadowing the environmental stimuli as traditional Pavlovian theory would predict, tastes seem to enhance the environmental aversion. The primary goal of the research is to analyze some of the factors contributing to the potentiation effect by studying conditioned activity of rats. This dependent measure has never been employed in previous studies of potentiation. Other procedures will utilize standard methods of taste-aversion research. Because this phenomenon seems to represent an adaptive learning capacity in foraging animals, this research will be important in our understanding of the evolutionary forces that have shaped feeding behaviors. Thus, in addition to revealing more about the mechanisms by which potentiation operates, this work should also provide the cornerstone for subsequent studies of foraging responses in semi-natural situations. Moreover, this work might prove an effective model of conditioned nausea reactions in cancer chemotherapy patients and may suggest behavioral treatment regimens to offset the environmental aversions responsible for this disruptive conditioning.